body {
  $menuWidth: 300px;
  $headerHeight: 50px;
  $footerHeight: 20px;
  $contentHeight: calc(100% - #{$headerHeight}-#{$footerHeight});
  .header {
    width: 100%;
    height: $headerHeight;
    background-color: aqua;
    position: absolute;
    top: 0;
  }
  .content {
    width: 100%;
    height: $contentHeight;
    position: absolute;
    left: 0;
    top: $headerHeight;
    bottom: $footerHeight;
    .menu {
      width: $menuWidth;
      height: 100%;
      background-color: blue;
      float: left;
      transition: 0.7s;
    }
    .menu-hide{
      margin-left: -$menuWidth;
    }
    .menu_expand{
      position: fixed;
      top: 50%;
      left: $menuWidth;
      width: 14px;
      height: 50px;
      z-index: 999;
      background-color: #f5f5f5;
      cursor: pointer;
      transition: 0.7s;
      &::before{
        content: "";
        width: 0;
        height: 0;
        border-top: 8px solid transparent;
        border-right: 10px solid #ab9561;
        border-bottom: 8px solid transparent;
        position: absolute;
        top: 0;
        bottom: 0;
        left: 0;
        right: 0;
        margin: auto;
      }
    }
    .menu_close{
      left: 0;
      width: 20px;
      &::before{
        transform: rotate(180deg);
      }
    }
    .page-content {
      width: 100%;
      height: 100%;
      padding-left: $menuWidth;
      background-color: aliceblue;
    }
    .page-content_expand{
      width: 100%;
    }
  }
  .footer {
    width: 100%;
    height: $footerHeight;
    background-color: beige;
    position: absolute;
    bottom: 0;
    text-align: center;
  }
}